Mushroom spawn will naturally develop a white (or yellow for Chicken of the Woods) mold-like layer called mycelium. This branching network of threads is the primary body of fungi, or vegetative structure. (A good analogy is to imagine mycelium like an apple tree, and a mushroom like an apple growing from it.)
Seeing mycelium growing throughout your bag is normal and indicates healthy mushroom spawn. However, if your spawn looks green or black, the culture may be contaminated and should be discarded. You can reach out to us for confirmation.
Healthy spawn bags have different amounts of mushroom culture visible depending on the species. (For example, lion’s mane has a wispy and faint mycelium and looks uncolonized.) Often, mycelium is broken up in shipping, so it can appear less myceliated. Let it sit for a few days and it should bounce back.